Page 16 - Introduction to Paleobiology and The Fossil Record

PALEONTOLOGY AS A SCIENCE 3
any modern organism (see Chapters 9–12).
Just imagine land animals 10 times the size
of elephants, a world with higher oxygen
levels than today and dragonfl ies the size
of seagulls, a world with only microbes, or
a time when two or three different species
of humans lived in Africa!
3 Climate and biodiversity change. Think-
ing people, and now even politicians, are
concerned about climate change and the
future of life on Earth. Much can be
learned by studying the modern world,
but key evidence about likely future
changes over hundreds or thousands of
years comes from studies of what has
happened in the past (see Chapter 20). For
example, 250 million years ago, the Earth
went through a phase of substantial global
warming, a drop in oxygen levels and acid
rain, and 95% of species died out (see
pp. 170–4); might this be relevant to
current debates about the future?
4 The shape of evolution. The tree of life is
a powerful and all-embracing concept (see
pp. 128–35) – the idea that all species
living and extinct are related to each other
and their relationships may be represented
by a great branching tree that links us all
back to a single species somewhere deep in
the Precambrian (see Chapter 8). Biolo-
gists want to know how many species there
are on the Earth today, how life became so
diverse, and the nature and rates of diver- the animal itself – how big was it, what were
sifications and extinctions (see pp. 169–80,
534–41). It is impossible to understand
these great patterns of evolution from
studies of living organisms alone.
5 Extinction. Fossils show us that extinction
is a normal phenomenon: no species lasts
forever. Without the fossil record, we
might imagine that extinctions have been
caused mainly by human interactions.
6 Dating rocks. Biostratigraphy, the use of
fossils in dating rocks (see pp. 23–41), is
a powerful tool for understanding deep
time, and it is widely used in scientifi c
studies, as well as by commercial geolo-
gists who seek oil and mineral deposits.
Radiometric dating provides precise dates
in millions of years for rock samples, but
this technological approach only works
with certain kinds of rocks. Fossils are
very much at the core of modern stratig-
raphy, both for economic and industrial
applications and as the basis of our under-
standing of Earth’s history at local and
global scales.
PALEONTOLOGY AS A SCIENCE
What is science?
Imagine you are traveling by plane and your
neighbor sees you are reading an article about
the life of the ice ages in a recent issue of
National Geographic. She asks you how anyone
can know about those mammoths and saber-
tooths, and how they could make those color
paintings; surely they are just pieces of art, and
not science at all? How would you answer?
Science is supposed to be about reality,
about hard facts, calculations and proof. It is
obvious that you can not take a time machine
back 20,000 years and see the mammoths and
sabertooths for yourself; so how can we ever
claim that there is a scientific method in pale-
ontological reconstruction?
There are two ways to answer this; the fi rst
is obvious, but a bit of a detour, and the second
gets to the core of the question. So,
to justify those colorful paintings of extinct
mammals, your first answer could be: “Well,
we dig up all these amazing skeletons and
other fossils that you see in museums around
the world – surely it would be pretty sterile just
to stop and not try to answer questions about
its nearest living relatives, when did it live?”
From the earliest days, people have always
asked questions about where we come from,
about origins. They have also asked about the
stars, about how babies are made, about what
lies at the end of the rainbow. So, the fi rst
answer is to say that we are driven by our insa-
tiable curiosity and our sense of wonder to try
to find out about the world, even if we do not
always have the best tools for the job.
The second answer is to consider the nature
of science. Is science only about certainty,
about proving things? In mathematics, and
many areas of physics, this might be true. You
can seek to measure the distance to the moon,
to calculate the value of pi, or to derive a set
of equations that explain the moon’s infl uence
on the Earth’s tides. Generation by genera-
tion, these measurements and proofs are tested
and improved. But this approach does not
work for most of the natural sciences. Here,